Chemical reproduction systems

ABSTRACT

Methods for chemical reproduction of images are provided comprising distributing iodate crystals in conformance with the image on a master sheet, transferring a portion of the iodate crystals in image configuration to a copy sheet which has been sensitized with reagents capable of reacting with the iodate crystals to form colored complexes, and contacting the latent image so formed on the copy sheet with moisture to develop a colored image on the copy sheet conforming to the latent image.

Iliteel @tates atent Palermiti et al. Dec. 3, 1974 [54] CHEMICALREPRODUCTION SYSTEMS 3.246.148 4/l966 DeTroeyer et al 101/469 UX3,386,379 6 1968 G dl h l. 101 469 751 Inventors: Frank M. Palermiti,Pittsford; a

Eugene P. Goldberg, Rochester, OTHER PUBLICATIONS Welcher, F. 1., 6a.Standard Methods of Chemical Analysis, om Ed., Vol. II, Part A, 1963,Van Nostrand [73] Assignees: Xerox Corporation, Rochester, NY. 276 & 277only i [22] Filed: July 10, 1970 Primary Examiner-David Klein [21] Appl.No.: 54,023 ABSTRACT Methods for chemical reproduction of images arepro- [52] Cl 101/470 101/473 63 vided comprising distributing iodatecrystals in confor mance with the image on a master sheet, transferring[51] Int. Cl 341m 5/00 a portion of the iodate crystals in imageconfiguration [58] Field of Search 101/469 to a copy sheet which hasbeen sensitized with tea. gents capable of reacting with the iodatecrystals to form colored complexes, and contacting the latent [56]References Cited image so formed on the copy sheet with moisture toUNITED STATES PATENTS develop a colored image on the copy sheetconforml,642,774 9/1927 Grange lOl/DlG. 1 ing to the latent image.2,254,483 9/1941 Hess et al. l0l/472 X D 2,398,779 4/1946 Dalton et a].101/469 UX 2 Clams, N0 Drawings 2,873,668 2/1959 Klimkowski et al.101/469 CHEMICAL REPRODUCTION SYSTEMS This invention relates tomulticopy reproduction systems. More particularly, this inventionrelates to a chemical reproduction system which gives rise to achromogenic chemical reaction to yield legible copy.

The ability to conveniently and rapidly make multiple copies has becomea sine qua non in all fields of business, education, government andscience. Existing methods of producing multiple duplicates of originalcopy such as xerography, photo-copying, thermal and diazo processesgenerally require the use of complex and expensive equipment. Lesssophisticated duplicating processes, such as spirit orstencil-duplicating are rather messy to operate and usually providecopies with poor image definition. Moreover, these latter processessuffer the additional disadvantage of requiring the preparation and useof a master or stencil which usually can only be conveniently used forone copying run. A significant effort has been expended to simplifyexisting copying systems and to reduce the cost per copy. It isdesirable to have simple copying systems which can be operated byunskilled labor at high speeds with good reliability and copy quality toproduce a large number of copies without destruction of the original ormaster.

Accordingly, it is an object of this invention to provide a simplecopying system which meets the requirements set forth hereinabove andovercomes the abovenoted deficiencies.

It is another object to provide a chemical copying system which yieldsmultiple copies adapted to become legible through a chromogenic chemicalreaction.

It is still another object to provide a multicopying system based uponthe transfer of iodate crystals in image configuration from a mastersheet to a copy sheet containing a chromogenic co-reactant whereby theiodate is converted to a complex of intense color.

These as well as other objects are accomplished by the presentinvention, which provides a method for chemical reproduction of an imagecomprising the steps of distributing finely divided iodate crystals inconformance with the image on a master sheet, transferring the iodatecrystals in image configuration to the surface of a copy sheet, saidsurface containing a chromogenic coreactant, forming a latent image; andcontacting said surface with an aqueous fluid thereby developing coloron said copy sheet in conformance with the latent image.

The present invention utilizes the intense color generated uponformation of a chromogenic complex such as the starch/ iodine complex todevelop latent images which have been transferred from a master sheet toa copy sheet. Surprisingly, it has been found that iodate crystals ormixtures containing said crystals can be selectively adsorbed in imageconfiguration upon images exhibiting some residual tack. Generally, suchimages are formed with non-drying inks or with wax or polymer based inkswhich can be rendered slightly tacky by heating. Because of thestoichiometry of the chromogenic reactions involved, a uniquely highmultiplication factor is provided permitting an extremely large numberof copies to be obtained from one master sheet. Moreover, because of theleverage obtained by the stoichiometry, very little iodate need beadsorbed or transferred in order to successfully reproduce multiplecopres.

PREPARATION OF MASTER SHEET Several convenient methods can be employedto distribute iodate crystals in image configuration with the imagesought to be reproduced. It has been found'that non-drying or slightlydrying inks exhibit sufficient residual tack to cause iodate crystals toadhere thereto. Also, it has been found that images formed with wax orpolymer based inks can exhibit such tack upon slight heating or warming.In one embodiment, an iodate image can be obtained simply by dusting theoriginal to be reproduced with an alkali metal iodate, for example,sodium iodate, potassium iodate, lithium iodate and the like, such as bycascading finely divided iodate crystals over the image surface andthereafter removing the excess iodate from the non-image areas byvibrating the original as by flicking the sheet with the fingers or thelike. If desired, a mixture containing an iodate salt and one or moresolid chromogenic co-reactants or precursors thereof can be employed inlieu of the iodate salt alone. For example, a binary mixture of sodiumiodate and potassium iodate or a ternary mixture such as sodium iodate,potassium iodate and a solid organic acid such as citric acid can beemployed. When such mixtures are employed, the components are preferablypresent in amounts ranging from about 50 percent to about percent inexcess of the stoichiometric requirements to insure sufficient'transferof all components. Most preferably, an iodate salt alone is used.Because of the leverage obtained in the chromogenic reaction, verylittle iodate need be adhered to the image to provide successfulduplication. Alternatively, the iodate crystals can be coated on orimpregnated in a ribbon to form a typewriter ribbon and the iodate imageproduced directly on the master sheet by typing. In either of theseembodiments, offset lithographic techniques can be employed to transfera negative impression to an offset blanket from the original imageimpression on the master. The offset negative impression can then beemployed to produce positive copies on copy sheets brought into pressurecontact with the offset blanket.

If it is desired to employ direct lithographic techniques, a mastersheet can be prepared containing a negative 'or mirror reverse image ofthe image to be duplicated. This can be conveniently accomplished byplacing a sheet of paper or plastic such as a polycarbonate, polyolefin,vinyl polymer or the like against the iodate coated surface of asuitably prepared carbon-type paper and then typing or writing on theside of the sheet of paper or plastic which is not in contact with thecarbon-type paper. Since carbon paper is normally oleaginous, it can bedusted with an iodate salt to prepare a carbon-type paper suitable foruse in the present invention. The typing can be carried out with anordinary ribbon in the typewriter. The pressure of the type as thewriting takes place causes a mirror reverse or negative impression imagecontaining the iodate salt to be formed on the surface of the sheet incontact with the carbon paper coated with said iodate salt. This sheet,called the master sheet, can be placed with the iodate reverse imageface up on the drum of a-direct process duplicating machine and copiesmade in the manner hereinafter described.

Alternatively, a back-up sheethaving a waxy or oily surface such as onoil skin or wax paper can be substituted for the iodate coatedcarbon-type paper. In this embodiment, a mirror reverse or negativeimpression image is formed on the surface of the sheet in contact withthe waxy or oily surface of the back-up sheet. Thereafter, the waxy oroily reverse image can be dusted with an iodate salt to form a reverseiodate image master sheet which can be employed on a direct processduplicating machine.

IODATE IMAGE TRANSFER Once the iodate image is formed, by any of thevarious embodiments described above, it can be transferred either to anoffset blanket, such as a metal roll, and then from the offset blanketdirectly to copy sheets as in conventional offset lithography or, usingthe techniques described above to obtain a negative iodate impression,the impression can be transferred directly to copy sheets. In allinstances, however, transfer either to the offset blanket or to the copysheets can be obtained simply by pressure. Generally, a pressure betweenabout 75 and about 150 pounds per linear inch is sufficient. Preferably,pressures of 100 to 125 pounds per linear inch are employed. The mastersheet can be,

clamped to a master roll or fed into the nip formed by two abuttingrolls in pressure contact, one of said rolls acting as an offsetblanket. The offset roll, in turn, can be abutted by a copy roll inpressure contact. Copy paper can be fed into the nip between the offsetroll and the copy roll to receive the transferred image.

Because of the stoichiometry of the chromogenic reaction, only a smallamount of the iodate salt need be transferred either to the offsetblanket or directly to the copy paper to obtain duplication.Consequently, one pass of the master sheet across the offset roll isusually sufficient to transfer enough iodate for several copies to beobtained. The master can be reused in this manner several times. As aresult, one dustihg of the master conveniently provides a multiplicityof copies, generally from about 50 to about 100 copies can be obtainedin this manner.

SENSITIZATION OF COPY SHEETS In order to foster the chromogenicreaction, the copy sheets are sensitized by treatment with the othercoreactants or precursors thereof needed to generate a chromogeniccomplex. Since all of the reactants are or by proper selection can besolid in nature, the present invention offers a great deal offlexibility with respect to selection of the actual mode of operation.

For example, the starch-iodine complex is usually formed by in situgeneration of iodine in the presence of starch. Generally, this isaccomplished as follows:

XIg yStarch Complex (II) Since the reactants can all be selected toexist in the solid state, the iodate can be admixed with either or bothof the iodide and acid to form the dusting composition as describedhereinabove for use in preparation of the master sheet. Thus, forexample, the dusting composition can be a mixture of an alkali metaliodate and an alkali metal iodide and/or an organic acid such as citricacid, tartaric acid, gluconic acid, malic acid, oxalic acid, formicacid, lactic acid, gallic acid and the like. Similarly, the typewriterribbons or carbon-type papers can be prepared from such mixtures. Inmany instances, use of such mixtures in preparation of master sheets hasbeen found to reduce background deposits.

Precursors of such reactants can similarly be employed. Alkali metalsulfites, for example, can be admixed and transferred with the iodatesalt. Upon contact with an acid, the sulfite forms a bisulfite whichreacts with the iodate generating iodide as follows:

Thus, depending upon the selection of the components of the dustingcomposition, the remaining components can be employed in conjunctionwith starch to sensitize the copy sheets to the reaction. Mostconveniently, starch sized paper impregnated with the other co-reactantsor precursors thereof can be employed. For example, in a preferredembodiment wherein the image to be developed is formed solely of aniodate salt, a starch sized paper impregnated with an organic acid, suchas citric acid, and an inorganic iodide, such as potassium iodide, canbe convenientlyemployed. The copy paper can be prepared by immersingstarch sized paper in an alcohol, water or alcohol/water solution ofcitric acid and potassium iodide and thereafter drying the paper.

Similarly, the copy sheets can be sensitized with other chromogenicco-reactants which form colored complexes with iodate salts. Forexample, gallic acid or a mixture of gallic acid and a water or alcoholsoluble manganese salt such as manganous chloride form colored complexeswith iodates:

10;, gallic'acid brown complex (IV) 10;, gallic acid MnCl brownish-blackcomplex v Also, poly(vinyl pyrrolidone) (PVP) is a strong complexingagent for iodine and is capable of complexing iodine from inorganiciodine-containing salts such as iodates forming complexes which range incolor from light yellow to dark reddish-brown depending on theconcentration of iodine in the complex:

10; PVP yellow-reddish-brown complex (Vl) Thus, copy sheets can beconveniently sensitized by impregnation with aqueous and/or alcoholicsolution of such chromogenic co-reactants as gallic acid, gallic acidand manganous chloride, PVP or the iodide, acid and starch combinationdescribed hereinabove.

For purposes of effective sensitization, the sensitizing solution cancontain from about 1 percent by weight up to a saturated solution of thechromogenic coreactants. Generally, in solutions of gallic acid and amanganese salt, the manganese salt is present in amounts ranging fromabout 0.5 to about 5 percent by weight.

The copy sheets can be sensitized prior to use employing conventionaltechniques for applying a sensitizing composition as described above toa paper or plastic web such as roller coating, knife coating, spraycoating, immersion processes causing impregnation and the like.Alternatively, a continuous process can be employed to apply a surfacecoating of the sensitizing composition to previously untreatedconventional starch sized paper or to unsized paper depending upon thechromogenic reaction involved. A bath can be prepared of an aqueous,alcoholic or alcohol/water solution of the sensitizing component. Aseries of rolls can be employed to transfer a film of the solution tothe starch sized or unsized paper as it passes between one of said rollsand a compression roll. The surface of the paper or plastic which hasbeen wetted with the sensitizing solution can then be brought intopressure contact with an offset blanket or a master roll containing areverse image as in a conventional rotary duplicating machine. Thesolvents in the sensitizing solution volatize rapidly permitting theproduction of a large number of copies and permit rapid drying therebyreducing smearing. Whether the copy sheets are presensitized or arecontinuously sensitized, it has been found that with respect toreactions involving the starch-iodine complex, better results can beobtained if the copy sheets, once sensitized, are top-coated with a thinlayer of starch. Dusting the sensitized copy sheets with starch has beenfound most convenient.

IMAGE DEVELOPMENT Once a latent image has been formed on the copy sheetby transferring the iodate image of the original image to the sensitizedcopy paper, a visible image can be readily obtained on the copy sheet bydeveloping the latent image upon contact with moisture convenientlyprovided as by water, steam and the like. Preferably, an aliphaticalcohol such as methanol, ethanol, isopropanol, tert. -butanol and thelike can be admixed with the aqueous fluid to improve the volatility ofthe developer fluid. The alcohol/water solution can vary between aweight ratio of alcohol/ water of from about 1:10 to about :1.

If desired, the sensitization of the copy sheets can be omitted andsensitization and development can, instead, be conducted simultaneously.For example, with respect to the starch-iodine complex, the acid and/oriodide salt can be added to the developer solution. The iodate image canbe transferred to starch sized paper and the image rendered visible uponcontact with the developer solution containing the other co-reactants.

Preferably, however, the developer fluid comprises only water or awater/alcohol mixture. Only small amounts of moisture are required fordevelopment. In fact, development can occur by passing the latent imagethrough a heating zone maintained at temperatures ranging from about50C. to about 150C. and a relative humidity of from about 75 percent toabout 100 percent. Although, in general, it is considered preferable toemploy organic acids for sensitization, dilute solutions of mineralacids such as hydrochloric acid can be employed in the developercomposition thereby obviating the presence of an acid in the sensitizedcopy sheets.

When sensitization of the copy paper is conducted on a continuous basisby wetting a surface of the copy paper with the sensitizer composition,development can be conveniently conducted on a continuous basis bypassing the sensitized sheet containing the latent image through acurtain of steam obtained by directing a stream or plurality of streamsof steam transversely to the path of movement of the copy paper. Afterdevelopment in this manner, the copy sheets can be continuously airdried or forced dried such as by heating. in this manner, dry, developedcopies can be conveniently and rapidly obtained.

The following examples further define, describe and compare methods ofpreparing multiple copies in accordance with the present invention.Parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 A typewriter master prepared on a conventional typewriter wasplaced in a support frame. Sodium iodate powder was cascaded over thesurface of said master. Thereafter, the cradled master was turned upsidedown and shaken to remove excess powder. The sodium iodate powderadhered to the oleaginous image areas. The master was then passedthrough a set of metal rollers at a pressure of 100 pounds per linearinch resulting in an imagewise transfer of the sodium iodate to therolls in the form of a reverse image. The transfer of the sodium iodatepowder was only a partial transfer enabling the master to be reused tore-image the rolls a number of times.

Sensitized copy paper was prepared by treating a commercially availablestarch sized paper with a solution of the following composition:

5 gms. Citric acid 100 CC. 111 ethanolzl-hO i 1 gm. Kl

After treatment, the paper was allowed to dry. The sensitized paper waspassed through the rollers whereupon a partial transfer of the sodiumiodate in image configuration to the paper occurred. At this point, theimaged copy was not visible, i.e., a latent image in the form of sodiumiodate powder contained on the sensitized paper was formed. The latentimage was subsequently developed by spraying the paper with a fine sprayof water. The developed image was purple-black in appearance. Twentyimaged copy papers were prepared from the single imaging of the metalrollers by the master. In an identical manner, the master was employed atotal of four times to image the rolls thereby producing a total ofimaged copies made from a single dusting'of one master. Moreover, themaster can be repeatedly employed in this manner, since the duplicatingprocess is non-destructive of the master.

EXAMPLE 2 Employing the identical procedure described in Example 1, copysheets containing a latent image were developed by spraying said sheetswith steam.

EXAMPLE 3 Employing the identical procedure described in Example 1, copysheets containing a latent image were developed by passing said sheetsthrough a heated zone maintained at C. and at a relative humidity of 100percent.

EXAMPLE 4 A xerographic copy of the typewritten master employed inExample 1 was prepared using a 2400 Xerox Copier. The xerographic copywas warmed to render the image thereon slightly tacky. Thereupon,potassium iodate crystals were cascaded over the surface of said copy.The xerographic copy was then turned upside down and flicked with thefingers to remove excess iodate. The potassium iodate crystals adheredto the slightly tacky image areas of the xerographic sheet. The sheetwas then passed through a set of metal rollers at a pressure of aboutpounds per linear inch resulting in an imagewise transfer of thepotassium iodate to the rolls in the form of a reverse image. Thetransfer of the potassium iodate powder was only a partial transferenabling the xerographic sheet to be re-used a number of times tore-image the rollers.

Sensitized copy paper was prepared by treating a commercially availablestarch sized paper with a solution of the following compositions:

5 gms. citric acid 100 cc. 1:1 methanol: H

1 gram Kl After treatment, the paper was allowed to dry. The sensitizedpaper was passed through the rollers whereupon a partial transfer of thepotassium iodate in image configuration to the paper occurred resultingin the formation of a latent image on the copy sheet. The latent imagewas developed by exposing the latent image to a steam spray.

EXAMPLE 5 The following example illustrates a method of obtaining areverse iodate image which can be employed as a master sheet in a directlithographic process such as on a conventional rotary duplicatingmachine.

Ari oleaginous back-up sheet containing sodium iodate was prepared asfollows:

A coating composition containing:

12.5% carnauba wax 10.5% microcrystalline wax 12.0% petrolatum 15.0%mineral oil 50.0% sodium iodate was prepared by admixing the componentsand forming a hot melt at temperatures between about 8090C. The hot meltwas roller coated onto a suitable base sheet in weights of about 20pounds per 3,000 square feet.

The back-up sheet was placed in contact with a conventional bond papersheet and inserted into a typewriter. Typing was conducted on the bondpaper. The pressure of the typewriter keys caused transfer of the iodatecoating composition to the back side of the bond paper forming an iodatereverse image of the writing.

The bond paper containing the iodate reverse image was affixed to therotary drum of a conventional rotary duplicating machine.

Sensitized copy paper was prepared by immersing starch sized paper in abath comprising:

1.25 grams Kl 5.0 grams gallic acid 500 ml. 90% ethanol After immersionand impregnation of said copy sheets with the above sensitizingcomposition, the sheets were allowed to dry.

The sensitized copy sheets were fed into pressure contact with thereverse image on the master sheet resulting in the formation of a directlatent, i.e., an invisible image, on the copy sheets. The copy sheetswere subjected to a steam spray to develop legible images. In thismanner, 25 copies were obtained exhibiting good image quality.

EXAMPLE 6 Employing the procedure described in Example 5, a reverseimage master was prepared using the coating composition thereindescribed except said coating composition contained no iodate salt. Upontyping, the oleaginous back-up sheet formed an invisible oleaginousreverse image on the back side of the master sheet. The back side of themaster sheet was then dusted with a 1:4 potassium iodatezpotassiumiodide mixture. The mixture adhered to the oleaginous image areas andwas easily shaken off the non-image areas. The master sheet containingthe coated reverse image was fastened to the master roll of aconventional rotary duplicating machine.

Starch sized copy sheets containing no additional sensitizer were fedinto pressure contact with the master sheet forming direct latent imageson said copy sheets. The images were developed by application of a finespray of an aqueous solution containing 10 percent l-lCl. Twenty-fivesharply defined copies were thus obtained.

EXAMPLE 7 A conventional typewriter ribbon was thoroughly coated withsodium iodate by dredging the ribbon through a bed of the iodate salt.The ribbon was placed in a typewriter and employed in conventionalmanner to obtain a typed master sheet. The master sheet was fed betweena set of rotating stainless steel rollers under a pressure of 100 poundsper linear inch whereupon the iodate image was partially transferred tothe metal roller acting as an offset blanket.

Copy sheets were sensitized by spraying conventional starch sized paperwith a sensitizing composition containing:

1.25 grams Lil 2.50 grams boric acid 500 ml. 9:1 ethanol: water, anddrying said sheets.

The copy sheets were then fed between the nip formed by the offset rolland a stainless steel compression roll maintained under a pressure of100 pounds per linear inch whereupon imagewise transfer to the copysheets occurred. The copy sheets were developed by application of asteam spray. A total of copies were obtained.

EXAMPLE 8 Employing the procedure described in Example 1, a sodiumiodate image was transferred to an offset blanket.

Sensitized copy sheets were prepared by impregnating starch sized paperwith sodium sulfite. The copy sheets were then fed into pressure contactwith the offset blanket whereupon a direct latent image was formed uponthe copy sheets. The latent image was developed by spraying the copysheets with an aqueous 15 percent HCl solution.

This Example illustrates the in situ formation of lodide by reaction ofthe iodate salt with the bisulfite generated upon development of thelatent image containing both iodate and sulfite under acidic conditions.The iodide so generated reacts further with the residual iodate to formiodine and subsequently the starch-iodine complex.

EXAMPLE 9 The foregoing examples have illustrated various methodsinvolving dry transfer of an iodate salt to copy sheets containing aniodide and acid and various alternative embodiments thereof. Thisexample illustrates the use of wet transfer in accordance with thepresent invention.

The fluid tank of a typical spirit process duplicating machine wasfilled with the following solution:

12.5 grams K1 25.0 grams citric acid 400 ml. 1:4 ethanolzwater A mastersheet prepared as described in Example 5 was clamped to the drum of themachine. In operation,

the copy sheet, wet with the above solution, was brought into pressurecontact with the master sheet. Under these conditions, the master sheetwas also wet by the solution and wet transfer occurred from the mastersheet image areas to the copy sheet. With wet transfer, sensitizationand development occurs simultaneously. Because of the rapidity ofdevelopment in the technique, very little liquid was left to beevaporated from the copy sheet. Two hundred fifty copies were obtainedfrom the master sheet.

EXAMPLE 10 The fluid tank of a typical spirit process duplicatingmachine was filled with a saturated solution of gallic acid in 400milliliters of a 1:4 ethanolzwater solution containing 2.0 percent MnClA master sheet prepared as described in Example 5 was clamped to thedrum of the machine. In operation, an untreated copy sheet wet with theabove solution, was brought into pressure contact with the master sheet.Under these conditions, the master sheet was also wet by the solutionand wet transfer occurred from the master sheet image areas to the copysheet. With wet transfer, sensitization and development occurssimultaneously. Because of the rapidity of the development technique,very little liquid was left to be evaporated from the copy sheet. Inthis manner, one hundred copies exhibiting a sharp brownish-black imageon a white background were obtained from the master sheet.

EXAMPLE 1 l Employing the procedure described in Example with a bathcontaining a saturated solution of gallic acid in 400 ml. of a 1:4ethanokwater solution, seven copies exhibiting a sharp brown image on awhite background were obtained.

EXAMPLE 12 The procedure described in Example 5 was employed to obtain amaster sheet containing an iodate reverse image. The master sheet wasaffixed to the rotary drum of a conventional rotary duplicating machine.

Sensitized copy paper was prepared by immersing previously untreated,unsized bond paper in a bath comprising a saturated aqueous solution ofpoly(vinyl pyrrolidone). After immersion and impregnation of the copysheets with the above sensitizing composition, the sheets were allowedto dry.

The sensitized copy sheets were fed into pressure contact with thereverse image on the master sheet resulting in the formation of a directlatent image, i.e., an invisible image on the copy sheets. The copysheets were subjected to a steam spray to develop legible images. lnthis manner, twenty-five copies exhibiting a sharp dark reddish-brownimage on a white background were obtained.

Although specific materials and conditions were set forth in the aboveexemplary processes in making and using the various components andmethods of this invention, these are merely intended as illustrations ofthe present invention. Various other compositions and processes such asthose listed above may be substituted in the examples with similarresults.

Other modifications will occur to those skilled in the art upon areading of the present disclosure. These are intended to be includedwithin the scope of this invention.

What is claimed is:

l. A method for chemical reproduction of images by a chromogenicreaction of an iodate, an iodide, an acid, and starch comprising thesteps of:

distributing finely divided iodate crystals in conformance with an imageon a master sheet;

at least partially transferring the iodate crystals in imageconfiguration to the surface of a copy sheet, said copy sheet containingstarch, an alkali metal iodide, and an acid therein, to form a latentimage on said sheet; and,

contacting said sheet with steam to thereby develop color on said copysheet in conformance with the latent image.

2. A method for chemical reproduction of images by a chromogenicreaction of an iodate, an iodide, an acid, and starch comprising thesteps of:

distributing finely divided iodate crystals in conformance with an imageon a master sheet;

at least partially transferring the iodate crystals in imageconfiguration to the surface of a copy sheet, said copy sheet containingstarch, an alkali metal iodide, and an acid therein, to form a latentimage on said sheet; and,

developing color on said copy sheet in conformance with the latent imageby heating said sheet at temperatures between about 50C. and about 150C.in an environment maintained at a relative humidity of between about 50and percent.

1. A METHOD FOR CHEMICAL REPRODUCTION OF IMAGES BY A CHROMOGENICREACTION OF A IODATE, AN IODIDE, AN ACID, AND STARCH COMPRISING THESTEPS OF: DISTRIBUTING FINELY DIVIDED IODATE CRYSTALS IN CONFORMANCEWITH AN IMAGE ON A MASTER SHEET; AT LEAST PARTIALLY TRANSFERRING THEIODATE CRYSTALS IN IMAGE CONFIGURATION TO THE SURFACE OF A COPY SHEET,SAID COPY SHEET CONTAINING STARCH, AN ALKALI METAL IODIDE, AND AN ACIDTHEREIN, TO FORM A LATENT IMAGE ON SAID SHEET; AND, CONTACTING SAIDSHEET WITH STEAM TO THEREBY DEVELOP COLOR ON SAID COPY SHEET INCONFORMANCE WITH THE LATENT IMAGE.
 2. A method for chemical reproductionof images by a chromogenic reaction of an iodate, an iodide, an acid,and starch comprising the steps of: distributing finely divided iodatecrystals in conformance with an image on a master sheet; at leastpartially transferring the iodate crystals in image configuration to thesurface of a copy sheet, said copy sheet containing starch, an alkalimetal iodide, and an acid therein, to form a latent image on said sheet;and, developing color on said copy sheet in conformance with the latentimage by heating said sheet at temperatures Between about 50*C. andabout 150*C. in an environment maintained at a relative humidity ofbetween about 50 and 100 percent.